Higgs decays

 With the Higgs decaying directly into pairs of all massive particles, and through loop diagrams even into pairs of massless gluons and photons, the field of Higgs physics is large. After a discovery of a Higgs particle it will be important to detect the Higgs decay into several decay channels to check if the coupling strength is in proportion to the mass for all fermions as the standard model predicts.

The partial width of the Higgs to the dominant decay modes will be calculated analytically at the lowest order in the sections 2.3.1 to 2.3.4. The total width and the branching ratios are plotted in fig. 2.5 and fig. 2.6. They are calculated with the program HDECAY [15] which includes the dominant higher order corrections to the decay widths.

It is clear from the figure that branching ratios change dramatically across the possible range of the Higgs mass making it necessary to have different strategies for the Higgs identification depending on its mass.

  

Figure 2.5: The total width of the standard model Higgs. Note how the width approaches the value of the mass itself for a very heavy Higgs.

  

Figure 2.6: The branching ratio of a standard model Higgs for all decays with a branching ratio above 10^{- 6}.